This invention relates to a method of storing figure data inputted to a computer into a memory and retrieving the stored figure data and more particularly, to a figure retrieval method suitable for speed-up of retrieval of figures located at arbitrary positions.
JP-A-58-117077 is related to the present invention and proposes a method which uses two tables for retrieving figures, one being an address data table in which memory addresses for figure data are registered, and the other being a management table for determing the correspondence between a coordinate value representative of each cell which is a subspace of a figure space and a space address on the address data table at which addresses for figures that pass through a cell represented by coordinates is stored.
The prior art method however suffers various disadvantages as described below.
(1) When retrieving an arbitrary figure, it is necessary to consult or look up the management table which has a hierarchial structure of several grades, and this hinders the speed of figure processing.
(2) In order for the known retrieval method to be implemented effectively, addresses for figures contained in each cell have to be stored in the address data table in an orderly manner. Accordingly, when figures are newly added or figures are deleted, address data must be rearranged by sorting them so that addresses for new figures contained in each cell may be stored in an orderly manner.
(3) A figure is constituted by end points, node points and other points on a line. The known method has, however, no ability to selectively retrieve these points. For example, when only a point at a designated position on a line is desired to be retrieved, all of the candidate figures for that point must be retrieved, and thereafter the point sought must be extracted from the retrieved figures, thus degrading efficiency of retrieval.